The present invention relates to the releasing of glazing panels from supporting frames.
Reference to glazing panels should be understood to mean panels, screens, or windows of glass, plastics or any other material substantially transparent to wavelengths in the visible range of the spectrum.
Vehicle windscreens typically comprise either toughened glazing panels or laminated panel structures (typically comprising an outer glass layer, an inner glass layer and an interlayer, interposed between the outer and inner glass layers). The glazing panel may be tinted depending on preference to absorb specific wavelengths (particularly U.V.). For laminated windscreens the interlayer is typically tinted.
WO-A-9617737 discloses a method and apparatus for releasing bonded transparent screens (typically vehicle windscreens) from supporting frames to which they are bonded. The technique described uses laser energy directed to effect release of a screen from a frame. The technique is useful in that the laser energy is directed from the laser head to the bonding bead/glazing panel interface. Problems exist however in ensuring the required energy for release is delivered without overheating occurring in the body of the glazing panel, and also due to the nature of high energy laser apparatus there are inherent health and safety implications.
An improved technique has now been devised.
According to a first aspect, the invention provides a method of releasing a glazing panel from a frame to which the panel is bonded by interposed bonding material, the method comprising:
i) arranging light energy delivery means adjacent the glazing panel; and,
ii) operating the light energy delivery means to transmit light energy through the glazing panel to effect release of the glazing panel from the frame.
According to a second aspect the invention provides apparatus for releasing a glazing panel from a frame to which the panel is bonded by interposed bonding material, the apparatus comprising light energy delivery means arrangeable adjacent the glazing panel, and operable to transmit light energy through the glazing panel to effect release of the panel from the frame.
The light energy delivered is preferably of a wavelength substantially in the range 300 nm-1500 nm (more preferably in the range 400 nm-700 nm).
The light energy delivered is desirably pulsed according to a predetermined regime, preferably such that the pulse event duration (T on) is less than the inter-pulse interval (T off).
Desirably, a single pulse event of light energy delivered is of sufficient energy to effect separation of the glazing panel from the frame along a length of the bonding material.
The apparatus preferably includes a pulse forming network (which may include a capacitor and inductor arrangement) to drive the apparatus to produce a light pulse event. The apparatus preferably further comprises a trigger network for initiating operation of the pulse forming network.
Control means is preferably provided for controlling one or more apparatus parameters, preferably including the minimum permissible time elapsing between subsequent light pulse event. The control means is therefore preferably linked to the trigger network and/or the pulse forming network. A safety interlock is beneficially provided to reduce the risk of accidental initiation of a light pulse event. Preferred features of the safety interlock firing feature are described herein and in the appended claims.
It is preferred that means is provided for selectively adjusting the intensity of the light delivered. This is important in view of the differing degree to which various tinted glazing panels absorb light energy in the wavelength range contemplated. It is preferred that the apparatus includes different preset parameter settings which may be switched dependent upon the glazing panel tint to be de-bonded.
The light energy may be absorbed at the bonding material/panel interface either by the bonding material itself, or by an absorbing layer comprising the panel (such as the frit layer commonly found on vehicle glazing panels) or by a suitable light absorbent coating provided at the interface.
The light energy delivery means may be tracked about the periphery of the glazing panel, preferably at a predetermined rate dependent upon the power of the light energy delivery means and the pulse regime. Tracking means (preferably motorised tracking means) may be provided for this purpose.
Alternatively, the light energy delivery means may be hand held and positioned on the glazing manually by an operator. The delivery means may therefore have a manual trigger for initiating a light pulse when the delivery head is positioned to the operators satisfaction.
The apparatus preferably includes a safety interlock requiring at least two input devices to be actuated before light energy can be delivered from the delivery means. One of the input devices comprising the interlock may include the (main) manual trigger.
The apparatus preferably includes a delivery head (desirably carrying a light emitting device) from which the light energy is delivered, the delivery head beneficially including at least two input devices comprising the safety interlock, both input devices on the delivery head requiring actuation in order to enable light energy to be delivered from the delivery means.
The input devices comprising the safety interlock preferably comprise electrical input devices (such as switch means). Following actuation, the input devices comprising the interlock are preferably reset to a non-actuation state.
In one embodiment, the light energy delivered comprises a plurality of wavelengths, most preferably in the visible range of the spectrum. In one embodiment, it is preferred that the light energy is non-coherent. The light energy preferably attenuates rapidly with distance such that at a few centimeters (preferably less than 10 cm, more preferably less than 5 cm) from the energy delivery means the light energy density is significantly diminished from its maximum value (preferably falling to 50% maximum value or below).
The pulse regime is controlled, preferably such that a following light pulse event is inhibited in the circumstances that a preceding light pulse occurred within a predetermined time period. This prevents the apparatus being operated too rapidly (which may cause overheating of the glazing panel and or the gas discharge tubes). If the trigger (or other actuator) is held by the operator permanently actuated, the apparatus control provides that a series of pulse events are initiated at a predetermined time interval (typically greater than the minimum permitted time interval). The predetermined time interval is set by the control means and is dependent upon the discharge energy level set. Typically the predetermined time interval for xe2x80x98continualxe2x80x99 actuation in substantially in the range 0.5-5 s (more preferably 1-3 s). The higher is the pulse discharge energy set the longer is the minimum permitted interval and also the set level of the predetermined time interval for xe2x80x98continualxe2x80x99 actuation.
Desirably, the pulse regime is controlled such that a following light pulse event is inhibited if the time elapsing after a preceding light pulse event is greater than a predetermined time. This ensures that the device may not accidentally be left in an operable condition following use for a series of pulse events. The apparatus, for example may revert to a xe2x80x9cstandbyxe2x80x9d mode.
The energy delivered is preferably substantially in the range 100 Joules-10,000 Joules per pulse (more preferably in the range 500-1500 Joules per pulse). The pulse duration (T on) is preferably substantially in the range 1 xcexcs-100 ms, more preferably 1 ms-2 ms.
In a preferred embodiment, the energy delivery means comprises electrical gas discharge apparatus. Desirably, operation of the gas discharge apparatus is controlled to limit the pulse rate and/or duration of the light pulse.
The operation of the gas discharge apparatus is preferably controlled by:
i) charging a capacitor arrangement;
ii) initiating a trigger pulse to discharge the capacitor arrangement; and,
iii) discharging the capacitor arrangement through an inductor to the gas discharge apparatus.
Accordingly, for this preferred embodiment, apparatus according to the invention includes energy delivery means comprising electrical gas discharge apparatus.
The electrical gas discharge apparatus is controlled to limit the pulse rate of the light delivered. The apparatus preferably includes a pulse forming network having a capacitor and inductor arrangement in which the capacitor discharges through the inductor to drive the electrical gas discharge apparatus to produce a light pulse. The apparatus preferably further comprises a trigger network for initiating the capacitor of the pulse forming network to discharge.
Control means is preferably provided for controlling one or more apparatus parameters including the minimum permissible time elapsing between subsequent discharge pulses of the electrical gas discharge apparatus.
The electrical gas discharge apparatus preferably comprises an electrical gas discharge tube.
The electrical gas discharge apparatus desirably comprises a reflector (preferably a parabolic reflector) arranged to direct emitted light in a predetermined direction. The reflector preferably includes a reflective coating of a heat resistant material, preferably comprising a silver material.
The apparatus preferably includes a window through which emmited light is directed to pass through the glazing panel. The window may be omitted from the apparatus, and omitting the window has been found to beneficially aid in cooling of the light emitting devices (discharge tubes).
Desirably, the apparatus includes an edge guide (preferably xe2x80x9csnap fitxe2x80x9d releasable) arrangement to locate against a peripheral edge of the glazing panel. The edge guide assists an operator in manually positioning the apparatus correctly with respect to the bonding bead securing the glazing panel.
The apparatus may comprise focussing means arranged to focus the light energy at a predetermined location.
In one embodiment, the tracking and pulsed operation of the light energy delivery means may be coordinated such that subsequent light pulses overlap spatially a relevant portion of the glazing panel. Operation in this manner ensures good separation of the panel from the frame at the bonding material/panel inner layer interface.
It has been found that for glazing panels (particularly those including a tinted interlayer) operation of the light energy delivery means in pulsed mode provides benefits, because energy absorption in the body of the screen or panel (particularly at the interlayer of laminated glazing panels) is minimised.
In a preferred embodiment the apparatus comprises:
i) a light energy delivery head including an electrically operable light emitting element;
ii) a base unit remote from the delivery head, the base unit including electrical power supply for the light emitting element of the delivery head; and,
iii) flexible umbilical extending between the base unit and the delivery head permitting connection of the delivery head to the base unit.
The invention will now be further described in specific embodiments by way of example only and with reference to the accompanying drawings.